DIFFERENT WAYS OF SWIMMING 



which they bring together and then quickly separate 

 like the two plates of a pair of castanets. And if our 

 vision were still further extended, if the eye were able 

 to discern the microscopic animalcules which populate 

 this water in numbers at least 

 as great as those of the larger 

 creatures, we should see those 

 organisms, of minute size, move 

 about like the rest, swimming 

 by methods appropriate to their 

 structure, and beating the water 

 with the delicate little oscillat- 

 ing filaments, called vibratile 

 cilia, with which their bodies 

 are covered, either entirely or 

 in part. 



These repeated observations 

 lead to a definite conclusion. 

 The inexhaustible diversity of 

 the means which life employs 

 fills us with astonishment. For 

 a single functional action, swim- 

 ming, Nature works out and 

 reveals to us an incredible 

 wealth of different processes. 

 All sorts of devices are brought 

 into action. Every organ is 

 utilized, even those we should 

 least expect, or part of an organ 

 at any rate. But if we take 

 account of this diversity alone 

 we shall have an incomplete idea both of Nature and 

 her power. The tank in our aquarium, despite its 

 variety and the pleasure it affords us, gives us only a 

 small-scale representation of what is going on, freely 

 and on a far greater scale throughout the immensity 

 of the world of waters. It gives us a glimpse of the 

 life in those waters, but by no means of all life. 



53 ' 



Fig. 13. — Beroe. The animal, 

 a ctenophore, or comb-jelly- 

 fish, supports itself in the 

 water by means of its mov- 

 able flappers in rows, which 

 may be up to four inches 

 in length. 



